Arno Therapeutics to Present Positive, New Data Supporting the Potential of Onapristone in Endometrial and Breast Cancers at ASCO 2013 Annual Meeting
-- Data suggest presence of activated progesterone receptors in cells predict anti-progestin efficacy in endometrial and breast cancers; support further evaluation of onapristone

FLEMINGTON, N.J., May 15, 2013 /PRNewswire/ -- Arno Therapeutics, Inc. (OTCQB: ARNI), a clinical stage biopharmaceutical company focused on the development of oncology therapeutics, today announced new, positive data from three studies supporting its investigational compound onapristone to be presented at the American Society of Clinical Oncology (ASCO) 2013 Annual Meeting, which is being held May 31-June 4, 2013 in Chicago, Illinois.

Three separate preclinical studies support further investigation of onapristone - an orally-administered, investigational type 1 progestin receptor antagonist - and the development of a diagnostic test for the compound to identify patients with activated progesterone receptor (APR) as a potential biomarker of anti-progestin activity in endometrial and breast cancers. Recently, Arno Therapeutics announced its collaboration with Clarient Diagnostic Services Inc., a GE healthcare company, and leading provider of cancer diagnostic testing, to develop a diagnostic test to identify cancerous tumors with APR.

Onapristone is believed to work by binding to a protein called the progesterone receptor, thereby inhibiting dimerization, phosphorylation and DNA transcription activity. Progesterone receptors (PRs) are found in particular cells including those of the female reproductive tissue and some cancers.[i] The hormone progesterone binds to the receptors and may cause the cells to grow.i Preclinical studies have shown that PRs can play a role as drivers of malignant cell growth in certain cancers.

"We are pleased with the findings as they support the development of a diagnostic test for onapristone to help identify patients with activated progesterone receptors in endometrial and breast cancers who are most likely to benefit from treatment in these difficult-to-treat diseases," said Glenn Mattes, chief executive officer and president, Arno Therapeutics. "These data add to the growing body of knowledge indicating the potential of the compound to fill a high unmet medical need and we plan to pursue a global orphan drug designation in endometrial cancer."

The findings will be presented during the following poster presentations:

Determination of activated form of progesterone receptor (PR) in endometrial cancer (EC)Abstract #5602; Poster #53H Poster session: Monday, June 3; 8:00 – 11:45 a.m. CT; S Hall A2 The study evaluated 72 archived primary endometrial cancer samples to determine if APR can be identified in endometrial cancer and if a technique called immunohistochemistry (IHC) - developed to identify APR in breast cancer - could be used to identify APR positive cells in the endometrial cancer samples. It found that APR can be identified using antibodies specific to the A and B isoforms of the PR (PRA and PRB) and in approximately 40-45 percent of the endometrial cancer samples studied, there was a pattern consistent with the presence of APR positive cells. APR was defined as any tumor with more than 5 percent APR positive cells, which were identified by an aggregated PR nuclear distribution pattern. The study found that the IHC technique used to identify APR has the potential to be developed as a diagnostic test, which may help predict anti-progestin anti-tumor activity in patients with endometrial cancer.

Identification of the activated form of progesterone receptor (PR) in breast cancer (BC)Abstract #593; Poster #7HPoster session: Saturday, June 1; 1:15 – 5:00 p.m. CT; S Hall A2The study examined 303 archival breast cancer samples processed with PRA and PRB isotype specific antibodies to determine the feasibility of an IHC method for use as a biomarker test to identify the expression of APR in breast cancer. The developed IHC and analytical technique identified a nuclear morphology pattern consistent with APR positive cells in about a quarter (23% PRA; 22% PRB) of the breast cancer samples studied. The study also found that the IHC technique used to identify APR has the potential to be developed as a diagnostic test, which would help predict anti-progestin activity in patients with breast cancer.

Independent characterization by duel staining of progesterone receptor (PR) and estrogen receptor (ER) in breast cancer (BC)Abstract #596; Poster #8CPoster session: Saturday, June 1; 1:15 – 5:00 p.m. CT; S Hall A2 The study evaluated a total of 76 breast cancer samples to determine the expression of estrogen (ER) and progesterone receptors (PR) at the cellular level and to determine if ER and PR are expressed in the same breast cancer cells. Through a standard IHC testing procedure consisting of sequential double staining – the first with a duel anti-PR A/B antibody and ER antibody and the second with anti-ER and anti-PRA antibodies or anti-ER and anti-PRB antibodies – the study found that both ER and PR were expressed in the majority of tumors examined, but only a minority of the tumor cells expressed both receptors (ER and PR). ER and PR positivity was defined as 5 percent or more cells positive. Detailed findings were as follows:

In the initial testing of 13 tumors, 11 of 13 tumors were ER positive; 13 of 13 tumors were PR positive; seven of 13 tumor samples showed both ER and PR expression in 5-20 percent (median 5%) of the same tumor cells.

In the second series of testing with specific anti-ER and anti-PRA antibodies, both ER and PRA were expressed in 5-20 percent (median 5%) of the same tumor cells. Using the anti-ER and anti-PRB antibodies, ER and PRB expression was observed in 5-20 percent (median 10%) of the same tumor cells.

These findings support evaluating anti-progestins as a therapeutic target alone or in combination with anti-estrogens.

"Collectively, these new data represent a crucial step for Arno Therapeutics as they provide further evidence of the potential of onapristone as a personalized therapy across various female and male-related cancers and the potential for a diagnostic test to help identify the right treatment for the right patient at the right time," said Mr. Mattes. "We are committed to further evaluating onapristone as a treatment for select patients and are looking forward to initiating studies evaluating dosing and pharmacokinetics in patients later this year."

About Breast Cancer

In the United States, over 232,300 new cases of invasive breast cancer are expected to be diagnosed in women and over 2,200 new cases are expected in men during 2013. After cancers of the skin, breast cancer is the most frequently diagnosed cancer in women. More than 40,000 breast cancer deaths are expected in 2013, with the majority in women. Breast cancer ranks second as a cause of cancer death in women, following lung cancer. [ii]

About Endometrial Cancer

In the United States, about 49,500 cases of cancer of the uterine corpus (endometrium) - the body of the uterus - are expected to be diagnosed in 2013 and typically occur in the endometrium (lining of the uterus). About 8,200 deaths are expected in 2013.ii

About Arno Therapeutics

Arno Therapeutics is a clinical stage biopharmaceutical company developing innovative products for the treatment of cancer. Arno has exclusive worldwide rights to develop and market three innovative anti-cancer product candidates. These compounds are in clinical or preclinical development as product candidates to treat hematologic malignancies and solid tumors. For more information about the company, please visit www.arnothera.com.

Forward-Looking Statements

This press release contains forward-looking statements that involve substantial risks and uncertainties. These statements are often, but not always, made through the use of words or phrases such as "anticipates," "expects," "plans," "believes," "intends," and similar words or phrases. These forward-looking statements include, without limitation, statements regarding the timing, progress and anticipated results of the clinical development of onapristone, Arno's use of the diagnostic test being developed with Clarient in its planned Phase I trial of onapristone, as well as Arno's strategy, future operations, outlook, milestones, future financial position, future financial results, plans and objectives. We may not actually achieve these plans, intentions or expectations and Arno cautions investors not to place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. Various important factors could cause actual results or events to differ materially from the forward-looking statements that we make. Such factors include, among others, risks that the results of clinical trials will not support our claims or beliefs concerning the effectiveness of onapristone or any of our other product candidates, our ability to finance the development of our product candidates, regulatory risks, and our reliance on third party researchers and other collaborators. Additional risks are described in the company's Annual Report on Form 10-K for the year ended December 31, 2012. Arno is providing this information as of the date of this press release and does not undertake any obligation to update any forward-looking statements as a result of new information, future events or otherwise.